Rare Allotypes Research Articles

Molecular characterization of the archaic HLA-B*73:01 allele reveals presentation of a unique peptidome and skewed engagement by KIR2DL2.

HLA class I alleles of archaic origin may have been retained in modern humans because they provide immunity against diseases to which archaic humans had evolved resistance. According to this model, archaic introgressed alleles were somehow distinct from those that evolved in African populations. Here we show that HLA-B*73:01, a rare allotype with putative archaic origins, has a relatively rare peptide binding motif with an unusually long-tailed peptide length distribution. We also find that HLA-B*73:01 combines a restricted and unique peptidome with high-cell surface expression, characteristics that make it well-suited to combat one or a number of closely-related pathogens. Furthermore, a crystal structure of HLA-B*73:01 in complex with KIR2DL2 highlights differences from previously solved structures with HLA-C molecules. These molecular characteristics distinguish HLA-B*73:01 from other HLA class I alleles previously investigated and may have provided early modern human migrants that inherited this allele with a selective advantage as they colonized Europe and Asia.

Direct binding to antigen‐coated beads refines the specificity and cross‐reactivity of four monoclonal antibodies that recognize polymorphic epitopes of HLA class I molecules

Monoclonal antibodies with specificity for human leukocyte antigen (HLA) class I determinants of HLA were originally characterized using serological assays in which the targets were cells expressing three to six HLA class I variants. Because of this complexity, the specificities of the antibodies were defined indirectly by correlation. Here we use a direct binding assay, in which the targets are synthetic beads coated with 1 of 111 HLA class I variants, representing the full range of HLA-A, -B and -C variation. We studied one monoclonal antibody with monomorphic specificity (W6/32) and four with polymorphic specificity (MA2.1, PA2.1, BB7.2 and BB7.1) and compared the results with those obtained previously. W6/32 reacted with all HLA class I variants. MA2.1 not only exhibits high specificity for HLA-A*02, -B*57 and -B*58, but also exhibited cross-reactivity with HLA-A*11 and -B*15:16. At low concentration (1 µg/ml), PA2.1 and BB7.2 were both specific for HLA-A*02 and -A*69, and at high concentration (50 µg/ml) exhibited significant cross-reactions with HLA-A*68, -A*23 and -A*24. BB7.1 exhibits specificity for HLA-B*07 and -B*42, as previously described, but reacts equally well with HLA-B*81, a rare allotype defined some 16 years after the description of BB7.1. The results obtained with cell-based and bead-based assays are consistent and, in combination with amino acid sequence comparison, increase understanding of the polymorphic epitopes recognized by the MA2.1, PA2.1, BB7.2 and BB7.1 antibodies. Comparison of two overlapping but distinctive bead sets from two sources gave similar results, but the overall levels of binding were significantly different. Several weaker reactions were observed with only one of the bead sets.

Associação do alótipo raro C4A6 do sistema complemento com a doença cardíaca reumática

OBJETIVO: determinar se os alotipos do Fator B (BF), C2 e C4 (C4A e C4B) do sistema complemento poderiam ser marcadores para a doenca cardiaca reumatica (DCR) na populacao brasileira. METODOS: foram estudados 49 pacientes com DCR cronica. Os controles incluiram 65 individuos saudaveis, nao aparentados, pareados com a amostra dos pacientes de acordo com o sexo, idade e grupo racial. Os alotipos de BF, C2, C4A e C4B foram determinados por tecnicas-padrao, incluindo Western blot para a determinacao das variantes de C2 e C4, utilizando-se anticorpos monoclonais e policlonais. RESULTADOS: este estudo demonstrou um significante aumento do alelo raro C4A*6 (p=0,003 RR=11,85) e diminuicao de C4A*3 nos pacientes, quando comparados com os controles. Alem disso, alelos nulos de C4 e raros de C4 e BF foram observados com maior frequencia nos pacientes. CCONCLUSOES: considerando-se que foram avaliados somente pacientes com DCR, mais estudos serao necessarios para que se possa esclarecer se o alelo C4A6 pode ser um marcador da forma cardiaca ou da propria doenca.

Complement Component C6 Polymorphism: Novel Protein-Typing Technique and Distribution of Allotypes in Germany

The genetic polymorphism of human C6 was investigated in Germany using an improved technique: polyacrylamide gel isoelectric focusing and subsequent direct immunofixation with monospecific C6 antisera. Typing of C6 was performed on native serum samples from 1,775 unrelated persons. The gene frequencies in the population study were as follows: C6*A 0.6313, C6*B 0.3566 and the rare alleles C6*R 0.0121. In total, 8 rare allotypes were analysed. The gene frequencies obtained are in good agreement with those previously published.

Human C7 polymorphism: classification and association analysis with C6.

Polymorphism of the seventh component of human complement (C7) was investigated in Japanese. Four common and one rare allotypes were observed with desialized samples. Besides three common alleles,C7*1, C7*2 andC7*4, the existence of the hypomorphic variant,C7*3, was confirmed in Japanese with a polymorphic frequency. The recently describedC7*5 was found to correspond toC7*3 by comparing with reference samples. Moreover, a rare variant, tentatively named C7 7, was considered to be new. The population samples were also typed for C6. A rare variant, designated M92, was newly found. No significant associations between C6 and C7 alleles were found.

Analysis of multiple restriction fragment length polymorphisms of the gene for the human complement receptor type I. Duplication of genomic sequences occurs in association with a high molecular mass receptor allotype.

Human CR1 exhibits an unusual form of polymorphism in which allotypic variants differ in the molecular weight of their respective polypeptide chains. To address mechanisms involved in the generation of the CR1 allotypes, DNA from individuals having the F allotype (250,000 Mr), the S allotype (290,000 Mr), and the F' allotype (210,000 Mr) was digested by restriction enzymes, and Southern blots were hybridized with CR1 cDNA and genomic probes. With the use of Bam HI and Sac I, an additional restriction fragment was observed in 20 of 21 individuals having the S allotype with no associated loss of other restriction fragments. Southern blot analysis with a noncoding genomic probe derived from the S allotype-specific Bam HI fragment showed hybridization to this fragment and to two other fragments that were also present in FF individuals. Thus, an intervening sequence may be repeated twice in the F allele and three times in the S allele. A restriction fragment length polymorphism (RFLP) unique to two individuals expressing the F' allotype was seen with Eco RV, but the absence of persons homozygous for this rare allotype prevented further comparisons with the F and S allotypes. Analysis of the CR1 transcripts associated with the three CR1 allotypes indicated that these differed by 1.3-1.5 kb and had the same rank order as the corresponding allotypes. Taken together, these findings suggest that the S allele was generated from the F allele by the acquisition of additional sequences, the coding portion of which may correspond to a long homologous repeat of approximately 1.4 kb that has been identified in CR1 cDNA. We saw two other RFLPs with Hind III and Pvu II that were in linkage dysequilibrium with the Bam HI-Sac I RFLPs associated with the S allotype, and a third polymorphism was seen with Eco RI that was not in linkage dysequilibrium with the other polymorphisms. Thus, 10 commonly occurring CR1 alleles can be defined, making this locus a useful marker for the long arm of chromosome 1 to which the CR1 gene maps.

Phénotypes rares de l'alpha-1 antitrypsine: Etude d'un cas de variant M1X

Alpha-1 antitrypsin is the major component responsible for the normal alpha 1 band in human serum. Some genetic variants giving double alpha-1 band, may be associated with pathological process. In the course of a systematic screening of blood donors a double-band alpha-1 pattern was observed in a serum, due to the heterozygous expression of a genetic variant of the PI system. A possible clinical significance of the variant was investigated by characterizing it. The very rare allotype PI*X was identified and its frequency in the population of french blood donors was estimated around to one for 10,000.

Genetic polymorphisms of complement C6 and C7 in two Chinese populations.

Genetic polymorphisms of the complement components C6 and C7 in two Chinese populations (Beijing and Guangzhou) were investigated, using isoelectric focusing and immunoblotting technique. Three common and four rare allotypes of C6 were observed, and one of the rare allotypes was considered to be a new variant. Ten different patterns of C7 observed were classified into three homozygous and seven heterozygous phenotypes, indicating occurrence of four common and a new variant alleles. The new variants of C6 and C7 detected were designated as C6 B21 and C7 6, respectively. There was no statistically significant difference for C6 and C7 allele frequencies between the Beijing and the Guangzhou populations except forC7*4. TheC7*4 frequency was shown to be significantly higher in Beijing than in Guangzhou. No significant positive association between C6 and C7 alleles was found.

Genetic polymorphism of coagulation factor XIII B subunit in the Japanese population: description of three new rare alleles.

Polyacrylamide gel isoelectric focusing (PAGIEF) of neuraminidase-treated EDTA plasma samples followed by electroblotting with enzyme immunoassay was performed to further investigate coagulation factor XIII B subunit (FXIII B) polymorphism. In 435 Japanese subjects PAGIEF patterns of FXIII B were classified into five common and three rare allotypes. This suggested that the FXIII B*2 allele existed in the Japanese population in the same manner as in Caucasians. Three new rare allotypes were considered to be controlled by three rare alleles which were designated FXIII B*13, FXIII B*14, and FXIII B*15, respectively. The gene frequencies calculated from 435 Japanese subjects were FXIII B*1 = 0.2977, FXIII B*2 = 0.0184, FXIII B*3 = 0.6805, FXIII B*13 = 0.0011, FXIII B*14 = 0.0011, and FXIII B*15 = 0.0011, respectively.

An immunoblotting technique for complement C6 typing: three new variants.

An immunoblotting method for C6 typing was developed. After isoelectric focusing in thin-layer polyacrylamide gel, C6 proteins were transferred passively to nitrocellulose and then detected by a two-step enzyme immunoassay. A population sample of northeastern Japanese was investigated using this method. Three common and four rare allotypes were observed. The allele frequencies estimated from 495 blood donors were as follows:C6*A0.423, C6*B0.510, C6*B20.062, and rare alleles (91,M11, B4, andB5) 0.005. Three variants, 91,M11, andB5, were considered to be newly found. This method could be applicable to many other protein systems.

Polymorphism of the complement component C6 in Japanese.

Genetic polymorphism of human C6 was investigated in Japanese using isoelectric focusing and a specific haemolytic overlay method. Three common and six rare allotypes were identified. Five of these nine allotypes were reference-typed by the International Reference Laboratory. Five of the six rare allotypes were considered to be new. The allele frequencies were estimated in the population study as follows: C6 A 0.427, C6 B 0.483, C6 B2 0.076, and the rare alleles (A3, A21, M1, M2, B3, and B4) 0.014. Inheritance of the three common and the two rare (A3 and M1) allotypes was demonstrated in the family study. The patterns obtained by the pretreatment with neuraminidase are presented.

Comparison of rare PGM1 variants by isoelectric focusing and conventional electrophoresis: Identification of five new variants

AbstractA comparison of specimens tested in our laboratory for the red cell enzymes sub‐system PGM1 by isoelectic focusing and conventional electrophoriesis demonstrated 11 rare allotypes. In addition to the allotypes PGM, PGM, PGM, , and , we indengified five new variants: , , , , . Of the five new variants only and could be separated from common PGM1 variants on conventional elehoresis. Because of the unique banding patterns for the variants observed, it was found necessary to use both isoelectic focusing and conventional methods for proper identification. Due to the presence for several different momeclatures for naming PGM variants, it is felt that a universal nomenclature should be defined to deal with PGM variants using both methods of analysis.